


Changes

by heartspocky



Series: Was supposed to be Kinktober but is now more like Kinkmas 2019 [1]
Category: Kingdom Hearts
Genre: Age Difference, Alpha/Beta/Omega Dynamics, Anal Sex, Canon Universe, Dubious Consent, First Time, Inconsistent POV sorry, M/M, Mating Cycles/In Heat, PWP
Language: English
Status: Completed
Published: 2019-12-21
Updated: 2019-12-21
Packaged: 2021-02-25 23:08:34
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,655
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/21883504
Author URL: https://archiveofourown.org/users/heartspocky/pseuds/heartspocky
Summary: Ansem helps Riku through his first heat.
Relationships: Ansem Seeker of Darkness | Xehanort's Heartless/Riku
Series: Was supposed to be Kinktober but is now more like Kinkmas 2019 [1]
Series URL: https://archiveofourown.org/series/1576429
Comments: 9
Kudos: 56





	Changes

**Author's Note:**

> Prompts: ABO, first time, age gap.
> 
> Ambiguous timeline here (other than being post-KH1), so I've chosen not to mark warnings since it's not actually established how old Riku is. I guess that IS my warning--if the lack of an explicitly-stated age of 18+ is a dealbreaker for you, I get it and it's all good but you'll prob want to turn back.

Riku wasn't sure where Ansem had taken him; only that their impromptu destination came furnished with a bed and little else. He was woozy and overheated, dizzy and a little confused, but not altogether _bad_. At certain points, past the overwhelming sense of disquiet, it was even somewhat pleasant.

It was followed by a smell, a certain scent he couldn't place. He may have commented on it, absently, out loud. He wasn't sure. Thick and unfamiliar, it lingered in the back of his mind. Subtle, like the Dark. But... not quite. That was as unnerving as anything else; he'd long come to associate Ansem with that particular stench, but here he could hardly pick up on it—even with the Heartless, that foul _creature_ of the Dark, looming over him.

So close. Too close.

"Where—" Riku's voice was hoarse. Weak. He willed himself to continue, louder and bolder. "Where have you taken me?" 

Ansem placed a gentle hand on Riku's lower back and, though he started, Riku didn't push him away.

"To safety," Ansem responded easily, which only drove Riku's nerves closer to the edge.

"Like I'd believe that," he scoffed, fists clenched. Ready to fight at a moment's notice.

To fight.

...Why wasn't he fighting? 

They'd _been_ fighting then... something had happened. Something strange.

Right. He'd almost forgotten.

He'd been feeling off for a week, and it came to a head mid-battle: an all-encompassing dizziness overtaking him, knocking him off his feet. 

Ansem could have killed him right then and there. _Easily_. Could have dealt the final, fatal blow, and Riku would have been helpless to defend himself. But he didn't. 

Instead, Ansem had summoned his guardian, not to harm him, but to sweep him from the floor and carry him through a dark portal, away from the castle to... here, wherever _here_ was.

Leaving him vulnerable, confused, and just as alone as he ever was.

A horrible thought struck him.

"You—what did you do to me?" Riku barked.

Infuriatingly, Ansem regarded him with a hint of amusement. Voice smug.

"I would advise you to lie down, Riku."

Riku didn't pull away when Ansem touched him, urging him onto the bed. The brief moment of contact was electric, a pulse deep in Riku's body as if something had stirred; it was distracting, trying to decipher a _spark_ caused by the touch of his enemy. 

So he didn't dwell on it too long. He knew nothing would come out of it if he did. 

Besides, the bed was soft, plush, warm. Inviting.

But... not _right_.

Why wasn't it right? Why was everything in front of him so _wrong_?

He could fix it. He knew he could.

Without thought, Riku began rearranging pillows and blankets, working automatically, following vague feelings of _not quite_ and _almost_ and _right there_! It was so easy not to think, even with Ansem's eyes on him, even as the man watched with continued interest.

He worked until it was perfect, until it was _home_ , moved by a deep need to impress that he'd successfully squashed so long ago, or thought he had.... and for what? For who? 

For....

When Ansem finally spoke, it was as though he'd heard Riku's silent questioning. 

"As I thought," he murmured.

"What?" Riku growled.

"You're nesting."

"I'm _what_?"

Ansem didn't deign to address him, continuing as though Riku hadn't said a word. With an even tone, Ansem proceeded to expose him.

"I would assume you've experienced certain _changes_ , as of late. Small, seemingly insignificant differences—perhaps even imperceptible at times. Yet, at others, they call to you... to your heart; your mind; your body."

_His body._

Any urge to protest died right there. Riku shook his head fervently, feeling caught. 

"Nothing?" Ansem asked, though Riku knew this was simply a show put on for his benefit. "And yet, you're picking up scents... you're weak, starved for contact. It seems unlikely that such symptoms would escape your notice, but I suppose even your incredible astuteness has its limits." His lips curled into a sardonic smile. "A surprise, indeed."

"What are you _talking_ about?" Riku asked, dangerously close to whining, his stomach in knots. As far as he was concerned, the sooner Ansem came out with whatever he was trying to convey, the sooner Riku could tackle the issue head-on. The sooner he could fight. Or give in. 

Actually, _giving in_ sounded....

"Don't you see yet?" Right. Ansem was talking. Ansem had answers. Riku had to quit drifting, had to keep himself together. He blinked up at the man, late to absorb the question, and found that catching up didn't make much of a difference. He felt like he was being addressed in a different language by someone who kept raising their voice in an attempt to make him understand, but only making him feel dense. 

As Ansem's smile widened, Riku's stomach dropped.

"How very special, to be present for a newly-presented omega's first heat."

Riku shook his head again, unsure of the meaning of Ansem's words. _Omega, heat_... those weren't terms that rang any bells, not in any meaningful sense.

"...I... I don't understand..."

Ansem looked down at him, the smile wiped from his face, his newest expression impossible to read.

"Fascinating," he mumbled. "You truly do not know.... Somehow, you've reached maturity while remaining entirely ignorant of your own nature."

"What was that?" Riku returned, voice lacking an intended bite. Ansem's turn of phrase, though seemingly designed to keep Riku in the dark for as long as possible, could only be interpreted as an insult.Through his illness, Riku was bristling, body hot with anger, body hot. 

He wanted to lunge, he wanted to fight—no, not fight, but lunge _yes_ , he wanted something, he didn't know what—

Midway through the internal battle, Ansem's scent spiked, wiping Riku's mind to a near-blank. The feel of Ansem's hand, stroking his hair and face in wide motions, didn't help Riku regain any semblance of sense.

"You'll soon find that you will be rather unfit for your normal duties, Riku. But never you fear, I assure you it's natural. It's all perfectly natural...."

The stroking continued, softly and gently. Riku's eyes slipped closed for one jarring moment before he forced them open and alert, watchful. 

Letting his guard down like that could have been a fatal mistake, he knew that well. It didn't _feel_ like a mistake, but clearly that only meant that Riku couldn't quite trust himself at the moment. Not when Ansem was doing something to him he could barely describe, something that made him want to dive into depths he couldn't see. 

"In fact," Ansem continued. "You're luckier than you know... The thought of you struggling through your heat, alone and vulnerable, in the unbearable cold of the castle grounds, is one I can hardly endure... your suffering would have been beyond imagination." Beneath the sudden, unconvincing show of concern, Riku could feel Ansem's mounting excitement. A wave of dread washed over him—dread, and something else he couldn't identify. "Now, tell me how you feel."

"...tired. Too hot." Riku shifted, noting with mortification something warm and moist dripping down his thighs, leaving dark trails in the material of his pants. "Eugh... wet..."

Ansem nodded, unconcerned.

"Yes, that's to be expected—in preparation for mating. Allow me." He smiled wickedly, removing his gloves. Riku choked.

"Mating?!"

He pulled Riku's shirt over his head with ease, nuzzling into his neck and placing a kiss there, savoring the way the boy shivered and quaked in anticipation—though surely he didn't realize the extent of his desperation yet. 

Ansem reached for Riku's belt next, smile dropping when Riku pulled away, hesitating.

"Riku," he chided. In response, Riku spread out, eyes watchful. "You may feel compelled to fight at first; I would expect nothing less from you. But know that your very being is intended for exactly this: submission to Alphas such as myself. It is the only way."

"...that can't be..." Riku croaked, chest heaving, sweat collecting on the back of his neck, soaking strands of silver hair and plastering it to his body. "You're lying."

"Am I? You're becoming desperate for contact; overwhelmed by lust; overpowered by desire. Each of your senses are becoming more intense."

Riku wouldn't be able to argue with a straight face. Not with the way he was nuzzling into Ansem's touch, rubbing his face into Ansem's palm. That smell was so strong now... intoxicating. Riku wanted to be covered in it, so badly and so severely that he didn't feel the horror he knew he should when Ansem pulled away and his scent didn't entirely go with him.

"Your body is becoming softer and more pliant... you're beginning to produce slick, along with more—ah, _visual_ signs of arousal."

Riku didn't fight as Ansem stripped his pants away, reaching down the front of his underwear and pulling out his aching erection. He whined, wanting desperately to flee. 

Or, no—not flee. Wanting desperately to—to be held down and... what?

"Alpha," Riku tested the word out, heart racing, mind crying out: _this is wrong, it's wrong, it's wrong._ "...why..."

Ansem's eyes lit up, molten gold shining with victory; he had waited long enough. _They_ had waited long enough.

"You are _irresistible._ "

Riku's legs spread easily at Ansem's urging, slick pooling onto the covers, cock leaking. He was breathing as if he'd run a marathon, hyperalert as he allowed Ansem to finish undressing him. When he was no longer clothed, shirt, jeans, and underwear all discarded, Ansem pushed a finger inside. 

Riku was briefly struck breathless, mouth open in a desperate bid to draw air into his lungs. He hadn't expected any warning about what would happen once Ansem had stripped him, but neither had he expected this. More in shock than discomfort, Riku held still, trying to adjust quickly before anything else could be thrown at him. The room spun around him.

He wasn't sure if it was the sensation of something pressing inside his body this way, stimulating his nerves, that disoriented him so severely. Maybe it was the feeling of invasion as he was forced to adjust quickly to Ansem's finger, joined by a second too soon. It could have been the intimacy of the situation, the way Ansem's eyes met his when Riku dared to look up. Or that strong, intoxicating aroma quickly filling the room.

Abruptly, Ansem took Riku's shoulder and pushed him flat onto the mattress, unbuttoning coat and pants one-handed as he continued working Riku open. Riku squirmed beneath him, unused to being handled in this way and quick to startle. His legs were splayed wide, hips raised and back lifting off the mattress, desperate for more of this new feeling even as he struggled with it. 

Ansem removed his fingers, ignoring Riku's disappointed whines as he finished stripping from his own clothing.

"Present yourself to me," he commanded. 

Without thinking, Riku rolled onto his stomach, pressing his face to the pillow and shifting onto his knees, legs apart. He let out a gasp when he realized what he'd done; it had come so _naturally_. He'd known what that meant, when Ansem made his demand. Some base, instinctual part of Riku _knew_...

He clutched at the covers as Ansem touched him, squeezing his ass with both hands, running a thumb over his slicked entrance. He felt the pressure on the bed shift as though Ansem had braced himself, then the weight of something hot and thick between his cheeks. 

Riku moaned loudly, hole twitching, body buzzing with need. He wanted to beg, but the instinct overtaking him was warning him to obey. He knew that, whatever happened next, Ansem would do it only when he desired and would stop only when he determined they were finished. 

That was... wrong? 

No, Riku conceded. It was fine. More than fine.

"You poor boy..." Ansem's voice was soft, melodic, the meaning of his words lost in Riku's haze. Scents and touching, wetness and a strong, virile Alpha so close— "Poor, lowly omega... you've been denied from your true potential for far too long. Now I will give you the chance to right yourself. Tell me... what is it you desire?"

Riku gasped, trying to capture words from the jumbled images flying around his blurry mind.

" _You_. I want you to... to mate with me. No, that's not—I want..." He didn't have the vocabulary to describe what he was after, but Ansem knew. He _knew_ Ansem knew. "I want you to put it in me... till I'm full."

Fingers danced along the small of Riku's back, one hand clutched his hips, keeping him still.

"Is that so?"

"Yes," Riku cried. "Please!"

"As you wish."

Ansem pulled back, positioned himself, and _thrust_. Riku went stiff, teeth digging into the pillow, eyes clamped shut, breaths tearing out of him in laborious, shallow gasps, punctuated by tiniest whimpers. His body was tight, unaccustomed to even his own fingers, let alone the engorged length of an alpha in rut. 

Outside of heat, taking Ansem inside without working up to him would have been a challenge—a painful one, at that. As it was, the overflowing slick and increased elasticity Riku's heat provided allowed Ansem to fill him without struggle. 

Waves of hormones and buzzing pheromones filled Riku's senses, numbing him to some of that stretch and burn. There was still pain—maybe that was unavoidable—but the pleasure outshined any discomfort he felt tenfold. It overwhelmed him, instincts warring with one another, giving him no clear path but to chase the feeling.

He wanted to run.

He wanted to take charge, climb over him and ride Ansem's cock, setting a pace that was deliciously slow. 

He wanted Ansem to pound into him relentlessly, fast and hard, until he forgot everything except the feel of _Ansem, Ansem, Ansem_ , holding him down while deep inside.

He wanted to fight, to defeat him, destroy him for good. 

He wanted to roll over and be used, ready to obey any command. He wanted to be good and please his Alpha. 

He wanted _that_ more than anything. 

Ansem pet Riku's hair, remaining still as Riku shivered and choked and sweat. Riku tightened a little too much, and Ansem grunted as the grip became uncomfortably tense. The caress became a tug; gentle, a warning.

"This is what your body was made for, Riku. Remember that. Enjoy it."

"Sorry," Riku replied, voice hoarse. "It just—it hurts." 

The admission felt shameful. He wanted to be a good partner, but hoped that maybe Ansem would appreciate that his inexperience meant that he had never been sullied by another alpha.

He wasn't sure where that last thought had come from.

"To be expected. The pain will pass, lovely." 

"I don't want you to stop."

Ansem twisted his hand into Riku's hair and tugged. 

"I never intended to," he said. 

Riku whimpered again, attempting to prepare himself for the onslaught. His grip on the sheets tightened as Ansem drove into him, working him open the longer they went. Miraculously, each time Ansem pulled back, it became easier for him to slide back in. Deeper and quicker each time, with Riku arching his back and spreading his legs further in a blind attempt to help. 

Ansem rewarded him with a moment of reprieve, changing their rhythm to something quick and light—once, twice, three times, before returning to the brutality he much preferred. Riku let out a high, helpless moan as Ansem slammed against him, hips meeting Riku's ass. Over and over again, the slap of skin, Riku's moans, _squelch_. Less resistance. More friction.

Riku was getting used to him. It was a beautiful thing to behold.

 _Riku_ was beautiful to behold. Beneath the bluster and bravado lay the heart of a brilliant omega, and how he shined like this: submissive and honest and true.

Ansem grunted as Riku tensed once again, suddenly resisting as if privy to the alpha's thoughts. 

"Submit to your deepest desires, Riku... submit to me."

Riku swallowed hard, opening his mouth to pull more air into his overworked lungs.

"C-can I speak?" he gasped. Ansem quirked an eyebrow. The question was unexpected. 

"You may. You needn't ask."

"How... how long will this last? My heat?"

"Hmm." Ansem cocked his head, stretching languidly; all-too-comfortable prolonging the moment, making Riku anticipate, just as Ansem had for so many years. "Several days, surely. A week, if you're particularly fertile."

"Fertile? Why do you make it sound like—" Riku stopped there. A sudden knowledge overtook him, the same way it had at his first intoxicating taste of darkness. One that said, _This is how things are now, and there's no going back._

Ansem watched his epiphany take place. 

"The word you were looking for earlier," he purred, low and seductive and dangerous, "What you wanted... I believe it was this: you want me to breed you, Riku. You want nothing more than to be knotted, mated, and _bred_ like the inferior little creature you are."

Riku's fists curled into the sheets, his toes flexing. He was stifling his little trills, horror and artificial desire warring inside him. 

But Ansem was right—was always right, especially when Riku dreaded it most—and he did want all of that, wanted all of it and more. He wanted someone to fill him, use him, break him down and build him up again and again and again. He knew that if anyone could, it was Ansem. Somewhere in the back of his mind, he hated that knowledge.

He would deal with the consequences later.

"Yes!" he cried, lurching back, desperate for every inch of Ansem's cock. "Alpha—ah!—yes!"

Ansem grunted, his grip on Riku tightening as he spilled inside, knot swelling until he could no longer move. Locked to Riku, the omega wouldn't be able to escape even if he tried, even if he wanted to. 

He didn't.

Riku felt stuffed full, satisfied and warm, muscles twitching on their own to milk Ansem dry. It seemed to take ages—seed pumping inside him, surge after surge, slowing to a sustained trickle before it finally ceased. A rush of hormones made him feel high and a little dizzy, elated as he realized Ansem's knot would prevent even a drop of hot come from escaping. 

And his knot was _thick_. Riku was amazed by it, and by his own body for accommodating it—though he guessed it just about took him to his limit. 

He tested his theory by shifting his hips, very slightly, to find that it didn't budge. He didn't know how long this would last, but he did know that Ansem wouldn't be able to pull out too soon.

Satisfied, Riku pulled his hair to the side and bore his neck. Unaware of the meaning or significance to his own actions and urges, he simply acted on each little impulse as it came to him. It felt so much more natural than denial.

Except... no. That was wrong. He knew it was.

His mind filled with images unbidden, of a family, and future heats, and though he found himself gently rubbing his stomach, hopeful for something, he knew this would lead him somewhere... irreversible. 

"I can't," he said, voice weak. "You know we couldn't—Ansem, we _couldn't_ —" Riku couldn't even voice it. Ansem didn't respond, only stroking the hairs that stuck to the back of his sweaty neck. 

As a Heartless, Ansem was unable to produce offspring through this method. He would let Riku figure that out on his own.

Besides, even this brief distraction had the potential to derail plans long set into place; childrearing would all but throw a decade of hard work out the window. Not for the first time since Ansem realized the truth of Riku's nature—long ago, when they'd shared a body—he almost bemoaned Riku's overall importance to the fate of the worlds. The boy truly would make an ideal mate. A pretty little plaything to entertain him during his increasingly rare moments of downtime.

"I don't care how long my heat lasts, I'll figure it out how to deal with it on my own. This stops right here, Ansem. Once—" Riku shifted again, wincing. They really couldn't pull apart. "...once _this_ stops, I'll leave. Even if I have to escape. Even if it means destroying you."

Ansem was silent, remaining still until his knot deflated. He pulled back, noting no movement from the fickle omega who kept him so endlessly intrigued. In fact, Riku remained on display until he seemingly lost the strength to keep himself up, slumping onto his side like a puppet with cut strings. Warmth and the sweet scent of heat emanated from his being, a glance at his face revealed a glazed quality to his eyes. 

He'd fallen back into that useful, pheromone-induced trance much more quickly than Ansem would have expected. Ansem supposed if he were human, he too would find himself lost to his rut, mindless under the influence of Riku's heat. Fortunately he managed to keep his wits about him, though he couldn't deny that, even outside of heat, Riku had an... unusual effect on him.

"Would you still like to leave?" he asked. A moment passed in which Riku looked ready to speak, but ultimately said nothing. Then another.

Riku's hesitation said all Ansem needed to know. It wasn't a surprise, when he guided Riku onto his back to find that he was hard once again and already beginning to produce fresh slick—but it pleased him nonetheless. 

Gently he guided Riku onto his back, running his hands all over, feeling every inch of a body wet with sweat, semen and slick. Riku's legs parted without prompting, and he let out a low, beautiful purr.

"...I thought not. Now put your mind at ease, and give in."

Ansem pushed back into Riku's loose, overheated body, and Riku didn't resist.


End file.
